JPS61120884A - Radiation image converting method and radiation image converting panel for said method - Google Patents

Abstract

PURPOSE:To improve sensitivity in a radiation image converting method, by allowing a radiation passed through a material to be absorbed by a phosphor, irradiating the phosphor with electromagnetic waves and detecting radiation energy stored therein as fluorescence. CONSTITUTION:A radiation passed through a material or radiated from a material to be detected is allowed to be absorbed by a bivalent europium-activated alkaline earth metal halide phosphor of the formula. The phosphor is irradiated with electromagnetic waves in the wavelength region of 450-1,000nm to release radiation energy stored in the phosphor as fluorescence and the released fluorescence is detected. In the formula, MII is Ba, Sr, Ca; X, X' are different groups and each is Cl, Br, I; 0.1<=a<=10; 0<b<=3X10<-2>; 0<x<=0.2. Pref. the phosphor of the formula is incorporated in a radiation image converting panel.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of the Invention] The present invention relates to a radiation image conversion method and a radiation image conversion panel used in the method. More specifically, the present invention relates to a radiation image conversion method using a photostimulable divalent europium-activated alkaline earth metal halide phosphor, and a radiation image conversion panel used in the method.

[Background of the Invention] Conventionally, as a method for obtaining radiation images as images, so-called radiography uses a combination of a radiographic film having an emulsion layer made of a silver salt photosensitive material and an intensifying screen. law is being used. As an alternative to the conventional radiographic method, a radiation image conversion method using a stimulable phosphor is known, for example, as described in Japanese Unexamined Patent Publication No. 55-12145.

In this method, radiation transmitted through the subject or radiation emitted from the subject is absorbed into a stimulable phosphor, and then the phosphor is exposed to electromagnetic waves (excitation light) such as visible light or infrared rays in a time-series manner. By exciting the phosphor, the radiation energy stored in the phosphor is emitted as fluorescence (#primary luminescence), this fluorescence is read photoelectrically to obtain an electrical signal, and this electrical signal is converted into an image. .

The top-filling radiographic image conversion method has the advantage that it is possible to obtain an X-ray image with a rich amount of information with a much lower exposure dose than when conventional radiography is used. Therefore, this radiation image conversion method has a very high value especially in direct medical radiography such as X-ray photography for the purpose of medical diagnosis.

As a stimulable phosphor used in the above radiation image conversion method, a divalent europium-activated alkaline earth metal fluoride halide phosphor (M FX: Eu2+, but M
It has been proposed that the seal is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca, and X is a halogen other than fluorine. This phosphor is
After absorbing radiation such as rays, when exposed to electromagnetic waves in the visible to infrared region, it emits light in the near-ultraviolet region (M-extinction luminescence).

As mentioned above, the radiation image conversion method utilizes the photostimulability of the phosphor, but the stimulable phosphor itself, other than this divalent europium-activated alkaline earth metal fluoride halide phosphor, does not have much effect. unknown.

The present applicant has already filed a patent application for a radiation image conversion method and a radiation image conversion panel using a new divalent europium-activated alkaline earth metal/\rogenide phosphor represented by the following compositional formula (patent application 58-193162
issue).

Composition formula: M"X2・aMIIX'2:xEu2+(
However, MW is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X and Xo are at least one kind of /\logen selected from the group consisting of Cl, Br and I, And X#X'
and a is a numerical value in the range of 0.1≦a≦10.0, and X is a numerical value in the range of 0<x≦0.2). From its X-ray diffraction pattern as described in the above-mentioned application, the M ”F
It has been found that E u 2+ phosphor is a different type of phosphor with a different crystal structure, and after being irradiated with radiation such as X-rays, ultraviolet rays, and electron beams, it can be excited with electromagnetic waves in the wavelength range of 450 to 11,000 nm. Then, it exhibits near-ultraviolet to blue light emission (stimulated light emission) having an emission maximum around 40 S nm.

The radiation image conversion method using the radiation image conversion panel made of the above-mentioned stimulable phosphor is a very advantageous image forming method as described above, but it is important that the sensitivity of this method be as high as possible. Generally, the desired sensitivity of a radiation image storage panel to radiation increases as the stimulated luminance of the phosphor used therein increases. Therefore, it is desired that the stimulable phosphor used in the panel has as high a stimulable luminance as possible.

[Summary of the Invention] An object of the present invention is to provide a radiation image conversion method with improved sensitivity and a radiation image conversion panel used in the method.

In order to achieve the above object, the present inventor conducted various studies on the above-mentioned novel divalent europium-activated alkaline earth metal halide phosphor. As a result, it was discovered that a phosphor obtained by adding a specific amount of silicon monoxide to the phosphor exhibits high-intensity stimulated luminescence, which led to the present invention.

That is, in the radiation image conversion method of the present invention, the radiation is transmitted through the object. Alternatively, after the radiation emitted from the subject is absorbed by a divalent europium-activated alkaline earth metal halide phosphor represented by the following compositional formula (I), this phosphor is exposed to electromagnetic waves in the wavelength range of 450 to 11,000 nm. It is characterized in that by irradiating the phosphor, the radiation energy stored in the phosphor is emitted as fluorescence, and this fluorescence is detected.

Composition formula (I): M"X2++aM"X'2ebSiO:xEu2+...
・CI) (However, Ml is at least one alkaline earth metal selected from the group consisting of Ba, Sr, and Ca:
and Xo are at least one kind of halogen selected from the group consisting of Cl, Br and I, and
Hong Furthermore, the radiation image storage panel of the present invention is a radiation image storage panel substantially composed of a support and a stimulable phosphor layer provided on the support. , the stimulable phosphor layer contains a divalent europium-activated alkaline earth metal halide phosphor represented by the above compositional formula (I).

The present invention enables the 'j'lt phosphor to emit Q-rays such as X-rays by adding a specific amount of -silicon oxide to the novel divalent europium-activated alkaline earth metal halide phosphor.
This method was completed based on the new finding that stimulated luminescence brightness is significantly increased when excited with electromagnetic waves in the wavelength range of 450 to 11,000 nm after irradiation with A-rays.

Therefore, by using the divalent europium-activated alkaline earth metal l\halogenide phosphor represented by the above compositional formula (I), the sensitivity of the radiation image conversion method can be improved. Furthermore, the radiation image conversion channel of the present invention made of the above-mentioned phosphor exhibits significantly improved sensitivity.

[Structure of the Invention] The divalent europium-activated alkaline earth metal halide phosphor used in the present invention has a composition formula (): % formula % (where M![ is selected from the group consisting of Ba, Sr, and Ca). at least one alkaline earth metal;
Both X and Xo are at least one kind of halogen selected from the group consisting of Cl, Br, and , b is a numerical value in the range of o<b≦3×10−”, and X is a numerical value in the range of O<x≦0.2).

From the viewpoint of stimulated luminance in the phosphor represented by the above compositional formula (I), -b representing the amount of silicon oxide (Sin)
Preferably, the value is in the range to-'≦b≦10'',
In addition, M ” X 2 and M ” in composition formula (I)
The a value representing the ratio with X'2 is preferably in the range of 0.25≦6.0, more preferably 0.5≦a
≦2.0, and the X value representing the activation amount of europium is preferably in the range of 10'≦X≦10-''.

Ba, which is an example of a phosphor represented by the above compositional formula (I)
In the CJ12.BaBr2e bsio:0.001Eu phosphor, the b value representing the amount of monomorphic silicon in the phosphor and the stimulated luminance have a relationship as shown in FIG.

FIG. 1 shows BaCu2eBaBr211bSiO:0.
001E u ”b value and stimulated luminance of phosphor [
After irradiating with 80KVp X-rays, semiconductor laser light (7
80 nm)]. As is clear from Fig. 1, BaCJ12 eBa where b
Br2 * bsio:0.001Eu2+ phosphor is
-B value in 6 divalent europium-activated alkaline earth metal halide phosphors used in the radiation image conversion method of the present invention, which exhibits stimulated luminescence with higher brightness than phosphors to which silicon oxide is not added (b=o) It is based on this fact that the range of 0b≦3XIO- is defined.

Furthermore, from FIG. 1, it is clear that a phosphor having a b value particularly in the range of to-'≦b≦10-2 exhibits extremely high-intensity stimulated luminescence.

For divalent europium-activated alkaline earth metal halide phosphors used in the present invention in which Ml, X, It has been confirmed that there is a similar trend.

The stimulated emission spectrum and the stimulated excitation spectrum of the divalent europium-activated alkaline earth metal halide phosphor represented by the above compositional formula (I) are described in the specification of Japanese Patent Application No. 58-193162, respectively. The stimulated emission spectrum and stimulated excitation spectrum of the divalent europium-activated alkaline earth metal halide phosphor are almost the same. The wavelength range of the stimulated excitation spectrum is as wide as 450 to 11,000 nm, and therefore, in the radiation image conversion method of the present invention using this phosphor, the wavelength of the excitation light can be changed appropriately. That is, it becomes possible to appropriately select the excitation light source depending on the purpose. For example, the photostimulation excitation spectrum of the above phosphor is about 11
000n, it is possible to use a compact semiconductor laser (having an emission wavelength in the infrared closed region) as a stimulable light source, which is small and has a low driving power. It becomes possible to downsize the. In addition, from the viewpoint of the brightness of stimulated luminescence and the interaction with emitted light, it is preferable that the excitation light in the radiation image conversion method of the present invention is an electromagnetic wave in the wavelength range of 500 to 850 nm.

The divalent europium-activated alkaline earth metal halide phosphor represented by the above compositional formula (I) can be produced, for example, by the production method described below.

First, as raw materials for the phosphor, 1) at least two alkaline earth metal halides selected from the group consisting of barium halide, calcium halide, and strontium halide, 2) -silicon fluoride, and 3) halide. At least one compound that is far from the group consisting of europium compounds such as , oxides, nitrates, and sulfates is provided. In some cases, ammonium chloride or the like may be used as a flux.

When producing a phosphor, first, using the above 1) alkali metal halide, 2) -silicon oxide, and 3) europium compound, the composition formula (■) is stoichiometrically determined.
: M"X2・aMIIX'2*bSiO:xEu...(
IT) (However, the definitions of Ml, x, x', a, b, and X are the same as above.) Weigh and mix to obtain a relative ratio corresponding to

The above mixture operation is carried out, for example, in the form of a suspension. Then, by removing water from the suspension of this phosphor raw material mixture, a solid dry mixture is obtained. This moisture removal operation is preferably carried out at room temperature or at a not very high temperature (for example, 200°C or less) by drying under reduced pressure, vacuum drying, or both.Of course, the mixing operation is limited to the above methods. Not.

Note that the silicon oxide in 2) above may be added to this dry mixture without being added to the weighed mixture of the phosphor raw materials.

Next, the obtained dry mixture is finely pulverized, and the pulverized product is filled into a heat-resistant container such as a quartz port or an alumina crucible, and fired in an electric furnace. The firing temperature is 4
A temperature in the range of 00 to 1300° C. is appropriate, and the firing time varies depending on the amount of the phosphor raw material mixture filled and the firing temperature, but in general, 0.5 to 6 hours is appropriate. As the firing atmosphere, a neutral atmosphere such as a nitrogen gas atmosphere or an argon gas atmosphere, or a weakly reducing atmosphere such as a nitrogen gas atmosphere containing a small amount of hydrogen gas or a carbon dioxide atmosphere containing -carbon oxide is used. When the europium compound used contains trivalent europium, the trivalent europium is reduced to divalent europium during the firing process.

It should be noted that a method may also be used in which the phosphor raw material mixture is fired once under the above firing conditions, the fired product is allowed to cool, is pulverized, and then re-fired (secondary firing). 400-80 under neutral or weakly reducing atmosphere
The firing is carried out at a firing temperature of 0° C. for 0.5 to 12 hours.

The powdered phosphor used in the present invention is obtained by the above baking. Regarding the obtained powdered phosphor,
If necessary, various general operations in the production of phosphors such as washing, drying, sieving, etc. may be further performed.

By utilizing the manufacturing method described above, a divalent europium-activated alkaline earth metal halide phosphor represented by the above-mentioned compositional formula CI) can be obtained.

In the radiation image conversion method of the present invention, the above compositional formula CI)
The divalent europium-activated alkaline earth metal halide phosphor represented by is preferably used in the form of a radiation image storage panel (also referred to as a stimulable phosphor sheet) containing it.

The basic structure of a radiation image storage panel is a support and at least one stimulable phosphor layer provided on one side of the support. The D-urinary phosphor layer consists of a t4-stimulable phosphor and a binder that contains and supports the stimulable phosphor in a dispersed state. Note that a transparent protective film is generally provided on the surface of the phosphor layer opposite to the support (the surface not facing the support) to protect the phosphor layer from chemical deterioration or Protects from physical impact.

That is, 1. Radiation image conversion method V of the present invention: uses a radiation image conversion panel having a phosphor layer made of a divalent europium-activated alkaline earth metal halide phosphor represented by the above composition formula (I). It is desirable to implement it.

In the radiation image conversion method of the present invention using the stimulable phosphor represented by the compositional formula (I) in the form of a radiation image conversion panel, the radiation transmitted through the subject or emitted from the subject is the radiation! ! The radiation is absorbed by the phosphor layer of the radiation image conversion panel in proportion to the radiation energy, and a radiation image of the subject or subject is formed on the radiation image conversion panel as an accumulated image of radiation energy. This accumulated image is 450~1
By excitation with electromagnetic waves (excitation light) in the wavelength region of 1000 nm, it can be emitted as stimulated luminescence (fluorescence), and by photoelectrically reading this stimulated luminescence and converting it into an electrical signal, the radiation energy can be extracted. It becomes possible to visualize the accumulated image.

The radiation image conversion method of the present invention will be specifically explained using the schematic diagram shown in FIG. 2, taking as an example an embodiment in which a stimulable phosphor represented by M11th order (I) is used in the form of a radiation image conversion panel. do.

In FIG. 2, 11 is a radiation generator such as X-rays;
2 is a subject, 13 is a radiation image conversion panel containing a stimulable phosphor represented by the above compositional formula (I), and 14 is an excitation for emitting the accumulated radiation energy image on the radiation image conversion panel 13 as fluorescence. 15 is a photoelectric conversion device that detects fluorescence emitted from the radiation image conversion panel 13; 16 is a device that reproduces the photoelectric conversion signal detected by the photoelectric conversion device 15 as an image; 17 is a reproduced image 18 is a filter for transmitting only the fluorescence emitted from the radiation image conversion panel 13 without transmitting the reflected light from the light source 14.

Although FIG. 2 shows an example of obtaining a radiographic image of a subject, the subject 12 itself emits radiation (
In this specification, this is referred to as a subject), it is not necessary to particularly install the bipedal radiation generating device 11, and the photoelectric conversion device 15 to the image display device 17 are used for radiation image conversion. It is also possible to convert the information emitted from the panel 13 in the form of fluorescence into any other suitable device capable of reproducing the information as an image in some way.

As shown in FIG. 2, when the subject 12 is irradiated with radiation such as xli from the radiation generating device 11, the radiation passes through the subject 12 in proportion to the radiation transmittance of each part of the subject 12. The radiation transmitted through the subject 12 firstly enters the radiation image conversion panel 13 and is absorbed by the phosphor layer of the radiation image conversion panel 13. That is, the radiation image conversion panel 13
- An accumulated image of radiation energy (a kind of latent image) corresponding to a radiographic image is formed on the image.

Next, using the light source 14 on the radiation image conversion panel 13,
When irradiated with electromagnetic waves in the wavelength range of 0 to 11000 nm, the accumulated radiation energy image formed on the radiation image conversion panel 13 is emitted as fluorescence. The emitted fluorescence is proportional to the intensity of the radiation energy absorbed by the phosphor layer of the radiation image conversion panel 13. This optical signal composed of the intensity of fluorescence is converted into an electrical signal by a photoelectric conversion device 15 such as a photomultiplier tube, and the image reproducing device 1
6, the image is reproduced as an image, and the image display device 17 displays this image.

The operation of reading out the image information accumulated in a radiation image conversion panel as fluorescence is generally performed by scanning a channel in time series with a laser beam, and transmitting the fluorescence emitted from the panel by this scanning through an appropriate light condenser. This is performed by detecting with a photodetector such as a photomultiplier tube and obtaining a time-series electrical signal.This readout is performed by pre-reading by irradiating low-energy excitation light to obtain images with better observation and interpretation performance. and a main reading operation by irradiation with high-energy excitation light (see Japanese Patent Laid-Open No. 58-67240). By performing this pre-reading operation, it is possible to suitably set the readout conditions for the main reading operation. There is an advantage that it can be done.

Further, for example, solid-state photoelectric conversion elements such as photoconductors and photodiodes can be used as photoelectric conversion devices (Japanese Patent Application No. 1986-86226, Japanese Patent Application No. +1-158-
86227, the specifications of Japanese Patent Application No. 58-219313 and Japanese Patent Application No. 58-219314, and Japanese Unexamined Patent Publication No. 1983
In this case, a large number of solid-state photoelectric conversion elements are configured to cover the entire surface of the panel,
The photoelectric conversion device may be integrated with the panel or placed close to the panel, and the photoelectric conversion device may be an in-sensor in which a plurality of photoelectric conversion elements are connected in a line. Alternatively, it may be composed of one solid-state photoelectric conversion element corresponding to one pixel.

In addition to a point light source such as a laser, the light source in the above case may be a line light source such as an array of one light emitting diode (LED), semiconductor laser, etc. arranged in a row. By performing readout using the fluorescent light, it is possible to prevent the loss of fluorescence emitted from the panel, and at the same time, increase the solid angle of reception and increase the S/N ratio. Further, since the obtained electrical signal is converted into a time series by electrical processing of a photodetector rather than by time-series irradiation of excitation light, it is possible to increase the readout speed.

The radiation image conversion panel from which the image information has been read is erased by irradiating it with light in the wavelength range of the excitation light of the phosphor or by heating it. It is preferable to do so (see 41, 1983-11392 and JP-A-5, 1983).
6-12599), by performing this erasing operation, it is possible to prevent the generation of noise due to afterimages when the panel is used next time. Furthermore, by performing the erasing operation twice, once after reading and immediately before the next use, it is possible to prevent the generation of noise due to natural radioactivity and perform erasing more efficiently (Japanese Patent Laid-Open No. 57-11
(See Publication No. 6300).

In the radiation image conversion method of the present invention, the radiation used to obtain a radiation transmitted image of the subject includes: - the phosphor exhibits stimulated luminescence when excited by the electromagnetic waves after being irradiated with the radiation; Any radiation can be used as long as it can be used. For example, commonly known radiation such as X-rays, electron beams, and ultraviolet rays can be used. Further, when obtaining a radiation image of the subject, the radiation directly emitted from the subject may be any radiation that is similarly absorbed by the phosphor and serves as an energy source for stimulated luminescence. Examples include gamma rays, alpha rays,
Examples include radiation such as beta rays and neutron rays.

As a light source of excitation light for exciting the phosphor that has absorbed radiation from the subject or the subject, 450 to 110
In addition to a light source that emits light with a band spectral distribution in the wavelength range of 00n, for example, an Ar ion laser-1K
Lasers such as r-ion lasers, He-Ne lasers, ruby lasers, semiconductor lasers, glass lasers, YAG lasers, dye lasers, and light sources such as light emitting diodes can also be used. Among these, lasers can irradiate a radiation image conversion panel with a laser beam with high energy density per unit area.
Among them, preferable lasers as excitation light sources used in the present invention are He-Ne lasers and Ar ion lasers in terms of stability and output.
Semiconductor lasers are preferred as excitation light sources because they are small, require low driving power, and can be directly modulated, making it easy to stabilize the laser output.

The light source used for erasing may be one that emits light in the excitation wavelength range of the stimulable phosphor; examples include tungsten lamps, fluorescent lamps, halogen lamps, and high-pressure sodium lamps. can.

The radiation image conversion method of the present invention includes: a storage section that absorbs and stores radiation energy in a stimulable phosphor; a photodetection (readout) section that irradiates the phosphor with excitation light and emits the radiation energy as fluorescence; It can also be applied to a built-in type radiation image conversion device in which an erasing section for emitting energy remaining in the phosphor is built into one device (Japanese Patent Application No. 57-84436 and Japanese Patent Application No. 58-6
6730), by using such a built-in device, a radiation image conversion panel (or a recording material containing a stimulable phosphor) can be reused, and a stable A homogeneous image can be obtained.

Further, by using a built-in type, the device can be made smaller and lighter, and its installation and movement become easier. Furthermore, by mounting this device on a mobile vehicle, it becomes possible to carry out circular radiography.

Next, a radiation image conversion panel used in the radiation image conversion method of the present invention will be explained.

As described above, this radiation image storage panel consists of a support and a divalent europium-activated alkaline earth metal halide phosphor provided on the support and having the composition formula CI) dispersed therein. and a stimulable phosphor layer comprising a supporting binder. The stimulable phosphor layer can be formed on the support-F, for example, by the following method.

Examples of binders for the phosphor layer include proteins such as gelatin,
Polysaccharides such as dextran, or natural polymeric substances such as gum arabic; and polyvinyl butyral, polyvinyl acetate, nitrocellulose, ethylcellulose, vinylidene chloride/vinyl chloride copolymer, polyalkyl (meth)acrylate, vinyl chloride/vinyl acetate Binders typified by synthetic polymeric materials such as copolymers, polyurethanes, cellulose acetate butyrate, polyvinyl alcohol, linear polyesters, etc. may be mentioned. Particularly preferred among such binders are nitrocellulose, linear polyester,
These are polyalkyl (meth)acrylates, mixtures of nitrocellulose and linear polyester, and mixtures of nitrocellulose and polyalkyl (meth)acrylates.

First, the above-mentioned particulate stimulable phosphor and a binder are added to a suitable solvent and mixed thoroughly to prepare a coating solution 7A in which the stimulable phosphor is uniformly dispersed in the binder solution. .

Examples of solvents for preparing coating solutions include lower alcohols such as methanol, ethanol, n-propanol, and n-butanol; chlorine-containing hydrocarbons such as methylene chloride and ethylene chloride; and acetone, methyl ethyl ketone, and methyl isobutyl ketone. Ketones; esters of lower fatty acids and lower alcohols such as methyl acetate, ethyl acetate, and butyl acetate; ethers such as dioxane, ethylene glycol monoethyl ether, and ethylene glycol monomethyl ether; and mixtures thereof.

The mixing ratio of the binder and the stimulable phosphor in the coating solution varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, etc., but generally the mixing ratio of the binder and the stimulable phosphor is 1. ．． :1 to 1:100 (weight ratio), and particularly preferably l:8 to 1:40 (weight ratio).

The coating liquid also contains a dispersant to improve the dispersibility of the phosphor in the coating liquid, and a dispersant to improve the bonding force between the binder and the phosphor in the phosphor layer after formation. Examples of dispersants used for such purposes include phthalic acid, stearic acid, caproic acid, lipophilic surfactants, etc., which may be mixed with various additives such as plasticizers. can. Examples of plasticizers include phosphate esters such as triphenyl phosphate, tricresyl phosphate, and diphenyl phosphate; and polyesters of polyethylene glycol and aliphatic dibasic acids, such as polyesters of triethylene glycol and adipic acid and polyesters of diethylene glycol and succinic acid.

The coating solution containing the phosphor and binder prepared as described above is then uniformly applied to the surface of the support to form a coating film of the coating solution.

This coating operation can be carried out using conventional coating means such as a doctor blade, roll coater, knife coater, etc.

As a support, an intensifying screen (
The material can be arbitrarily selected from various materials used as supports for (or intensifying screens) or materials known as supports for radiation image storage panels. Examples of such materials are:

Films of plastic materials such as cellulose acetate, polyester, polyethylene terephthalate, polyamide, polyimide, triacetate, polycarbonate, metal sheets such as aluminum foil, aluminum alloy foil, ordinary paper, baryta paper, resin coated paper, pigments such as titanium dioxide, etc. Examples include pigment paper containing polyvinyl alcohol and sizing paper containing polyvinyl alcohol.

However, in consideration of the characteristics and handling of the radiation image storage panel as an information recording material, a particularly preferred material for the support in the present invention is a plastic film. This plastic film may be kneaded with a light-absorbing substance such as carbon black, or may be kneaded with a light-reflecting substance such as titanium dioxide.The former is a high-sharp type of radiation image converter. The latter is a suitable support for radiation image storage panels of high sensitivity type.

In known radiation image conversion panels, a phosphor layer is provided in order to strengthen the bond between the support and the phosphor layer, or to improve the sensitivity or image quality (gacuity 1 graininess) of the radiation image conversion panel. A polymeric substance such as gelatin is coated on the surface of the support on the side to be coated to form an adhesion imparting layer, or a light reflective layer made of a light reflective substance such as titanium dioxide, or a light absorbing substance such as carbon black. The support used in the present invention, which is known to be provided with a light absorption layer, etc., can also be provided with these various layers, and the structure thereof may be determined depending on the purpose, use, etc. of the desired radiation image conversion panel. It can be selected arbitrarily.

Furthermore, as disclosed in JP-A-58-200200, in order to improve the sharpness of the obtained image, the surface of the support on the phosphor layer side (the surface of the support on the phosphor layer side) When an adhesion-imparting layer, a light-reflecting layer, a light-absorbing layer, etc. are provided, minute irregularities may be formed on the surface (meaning the surface thereof).

After forming the coating film on the support as described above, the coating film is dried to complete the formation of the stimulable phosphor layer on the support. The thickness of the phosphor layer varies depending on the characteristics of the intended radiation image conversion panel, the type of phosphor, the mixing ratio of the binder and the phosphor, and is usually 20 ILm to 1 mm. However, the thickness of this layer is preferably 50 to 500 pm.

In addition, the stimulable phosphor layer does not necessarily need to be formed by directly applying a coating liquid onto a support as described above; After forming a phosphor layer by coating and drying, the phosphor layer may be pressed onto a support, or the support and the phosphor layer may be bonded together using an adhesive.

The stimulable phosphor layer may be only one layer, but it may be two or more layers.In the case of multiple layers, at least one layer is a divalent europium-activated alkaline earth metal halide layer of composition formula (I). Any layer containing phosphor may be used.
A structure may be employed in which a plurality of phosphor layers are stacked so that the luminous efficiency with respect to radiation increases sequentially toward the surface of the panel, and either in the case of a single layer or a multilayer structure.

A known stimulable phosphor can be used in combination with the above phosphor.

Examples of such known stimulable phosphors include:

In addition to the above-mentioned phosphors, ZnS:Cu, Pb, BaO@xAl described in Japanese Patent Application Laid-Open No. 55-12142
2O3:Eu (however, 0.8≦X≦10), and MxS i02: A (however, M″′ is Mg, Ca, Sr, Zn, Cd, or Ba, and A
is (:e, Tb, Eu, Tm, pb, Tn, Bi, or Mn, and X is 0.5≦X≦2.5), as described in JP-A-55-12143. There is (B
al-x-y, Mgx, Cay) FX:
aEu8 (However, X is at least one of C, l, and Br, and X and y are 0,
．． and xy#0, and a is 10-6≦a≦5
10-2), and LnOX:xA described in JP-A-55-12144 (however, Ln is L
a.Y.

At least one of Gd and Lu, X is at least one of Cl and Br, A is Ce and Tb
and X is O<x<O, l
), and so on.

In a normal radiation image storage panel, as mentioned above, a transparent protective film is placed on the surface of the phosphor layer on the side opposite to the side that contacts the support to physically and chemically protect the phosphor layer. is provided. Such transparent protection n! 2 is also preferably installed for the radiation image conversion panel for undeveloped Ug1.

The transparent protective film may be made of a transparent material such as a cellulose derivative such as MS cellulose or nitrocellulose; or a synthetic polymeric material such as polymethyl methacrylate, polyvinyl butyral, polyvinyl formal, polycarbonate, polyvinyl chloride, or vinyl chloride-vinyl copolymer. It can be formed by coating the surface of the phosphor layer with a solution prepared by dissolving a polymeric substance in an appropriate solvent. Alternatively, it can also be formed by a method such as adhering a transparent thin film separately formed from polyethylene terephthalate, polyethylene, polyvinylidene chloride, polyamide, etc. to the surface of the phosphor layer using a suitable adhesive. The thickness of the transparent protective film thus formed is preferably about 0.1 to 20 μm.

In addition, JP-A-55-163500, JP-A-57-
As described in Japanese Patent No. 96300, etc., the radiation bonding and image conversion panel of the present invention may be colored with a coloring agent, and the sharpness of the image obtained can be improved by using six colors. Further, as described in Japanese Patent Application No. 4-4-146447, the radiation image conversion panel of the present invention may have white powder dispersed in its phosphor layer for the same purpose.

Examples and comparative examples of the present invention are described below. However, each of these aspects does not limit the invention.

[Example 1] Aqueous solution of barium bromide (B aB r2) (I, 55X
10=mol/g) 192, 7 g, kpi barium luminide a0 2) aqueous solution (I, 18X10-'
mat/g) 253.

5g, and an aqueous solution of europium bromide (EuBr3) (2,841X 10-'mol/ml) 2,11
ml was mixed. This aqueous solution was dried under reduced pressure at 60°C for 3 hours, and then further dried under vacuum at 150°C for 3 hours. After mixing, the mixture was filled into an alumina crucible, and the mixture was placed in a high-temperature electric furnace for firing. Firing was carried out at a temperature of 850"C for 1.5 hours in a carbon dihydride atmosphere containing -M carbon. After the firing was completed.

The fired product was taken out of the furnace and cooled. In this way,
- Divalent europium-activated barium chloride bromide phosphor containing silicon oxide (BaCl2・B aBr 2 e
O,001S i O:0.0OIE u”) was obtained.

[Example 2] In Example 1, the amount of -silicon oxide added was 0.2 mg.
A divalent europium-activated barium chloride bromide phosphor (BaCJL2eEa
Br2eO,0OOISjO: 0.001E u 2+
) was obtained.

[Example 3] In Example 1, the amount of -silicon oxide added was 17.5 m
By performing the same operation as in Example 1 except for changing to g, divalent europium activation 11! Bromide/Churium phosphor (BaC
u2 *BaBr2 *0. OIS iO:O,0OI
E u ”) was obtained.

[Comparative Example 1] In Example 1, by performing the same operation as in Example 1 except that silicon monoxide was not added to the phosphor raw material mixture, divalent europium and activated barium chloride bromide phosphors were prepared. (Ba0 sentence 2・B a B r 2 :O,
OO]E u 2+).

Next, each of the phosphors obtained in Examples 1 to 3 and Comparative Example 1 was irradiated with X-rays at a tube voltage of 80 KVP, and then the stimulated luminescence brightness when excited with semiconductor laser light (780 nm) was measured. The results are summarized in Figure 1.

FIG. 1 shows Ba0M2 eBaBr2 * bS i.

It is a graph showing the relationship between the silicon monoxide content (b value) and the stimulated luminescence luminance in +O,0OIE u 2+ phosphor.

As is clear from FIG. 1, B ac used in the present invention
u2 e B aB r2 e bS iO:0. oo
The stimulated luminance of the lEu'' phosphor is improved when the b value is in the range of o<b≦3X10-''. In particular, b (I
A phosphor in which ri is in the range lO-'≦b≦10-'' exhibits high-intensity stimulated luminescence.

[Example 4] Using each of the phosphors obtained in Examples 1 to 3 and Comparative Example 1, a radiation image conversion panel was manufactured in the following manner.

Methyl ethyl ketone is added to a mixture of a powdered divalent europium-activated barium chloride bromide phosphor and a linear polyester resin, and further nitrocellulose with a degree of nitrification of 11.5% is added to contain the phosphor in a dispersed state. After preparing the dispersion, tricresyl phosphate, n-butanol, and methyl ethyl ketone were added to the dispersion, and the mixture was thoroughly stirred and mixed using a propeller mixer to ensure that the phosphor was uniformly dispersed and that the binder and Mixing ratio with phosphor is 1 =
10. Prepare a dilute coating solution with a viscosity of 25 to 35 PS (25°C). Next, apply the coating solution onto a titanium dioxide-mixed polyethylene terephthalate sheet (support, thickness: 250 pm) placed horizontally on a glass plate. was applied evenly using a doctor blade. After coating 15, the support on which the coating film was formed was placed in a dryer, and the temperature inside the dryer was gradually raised from 25°C to 100°C to dry the coating film. In this way, a layer thickness of 250
A phosphor layer of 1 Lm was formed.

Then, a transparent film of polyethylene terephthalate (thickness: 12 pm, coated with a polyester adhesive) is placed on top of this phosphor layer with the adhesive layer side facing down. A film was formed.

In this manner, various radiation image conversion panels each comprised of a support, a phosphor layer, and a transparent protective film were manufactured.

A tube voltage of 8 was applied to each radiation image conversion panel obtained in Example 4.
After irradiating with 0KVp X-rays, semiconductor laser light (780
The sensitivity (N original emission brightness) of the panel when excited at 100 nm) was measured. The results are shown in Table 1.

Table 1 Relative sensitivity BaC: 12 * BaBr2 e 0.001SiO
:0.001Eu2+Panel using phosphor (Example 1) 143BaCl2a BaBr2 e 0.000
Panel using 1SiO:0.001Eu” phosphor (Example 2) 122BaCI2 * BaBr2 m 0
．． Panel using 0ISiO:0.0OIEu” phosphor (Example 3) 123BaCl2e BaBr2:0
．． Panel 1 using “001Eu” phosphor (Comparative Example 1)
00

[Brief explanation of the drawing]

FIG. 1 shows a specific example of the phosphor used in the present invention, TARE 6B.
acu 2 fist B aB r2 a bS i O:
It is a graph showing the relationship between the b value and the stimulated luminance in O,0OIEu2'+ phosphor. FIG. 2 is a schematic diagram illustrating the radiation image conversion method of the present invention. 11: Radiation generator, 12: Subject. 13: radiation image conversion panel, 14: light source, 15: photoelectric conversion device, 16: image reproduction device. 172 Image display device, 18: Filter patent applicant, Fuji Photo Film Co., Ltd. agent, Br. Yasuo Yanagawa, 1st figure, value agent 7: Approval - Ro 7, December 1982, 140 41, Commissioner of the Correction Agency, Shiga Gaku Tono, 1982 Patent Application No. 240453 2, Name of the invention: Radiation image conversion method and radiation image conversion panel 3 used in the method, Relationship with the person making the amendment case Name of patent applicant (520) Fuji Photo Film Co., Ltd. Company 4, agent address: Mitsuya Yotsuya Building 8, 2-14 Yotsuya, Shinjuku-ku, Tokyo
Floor ff (358) 1798/9 6, Number of inventions increased by amendment None 7, Subject of amendment Column 8 of “Detailed Description of the Invention” of the specification, Contents of amendment U! l] We will amend the "Detailed description of the invention" column in p: as follows. Note (I) +2 pages, 12 lines [i'o of 1, 25≦6.0j
is corrected as fo, 25≦a≦6.0. (2) Change the ff2.11m sentence J on page 37, line 17 to l11.
Corrected to 06trljj. (3) 0.75mgj on page 38, line 2, no, 88m
Correct as gj. (4) Fo on page 38, line 14, 2mgj as ffo,
Correct it to 1mgj. (5) 1r17.5mgJ on page 39, line 1 is 18.7
Correct it to 5mgj. More L

Claims (1)

[Claims] 1. After the radiation transmitted through the subject or emitted from the subject is absorbed by the divalent europium-activated alkaline earth metal halide phosphor represented by the following composition formula (I), this phosphor has a wavelength of 450 to 1000 nm. A method for converting a radiation image, comprising: emitting radiation energy stored in the phosphor as fluorescence by irradiating the phosphor with electromagnetic waves in a wavelength range of , and detecting the fluorescence. Composition formula (I): M^IIIX_2・a_M_IIIX'_2・b_SiO:x
_Eu^2^+...(I) (However, M^III is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr and Ca; X and X' are both CL, Br and At least one halogen selected from the group consisting of I,
and X≠X'; and a is 0.1≦a≦10.
It is a numerical value in the range of 0, and b is 0<b≦3×10^-^2
(X is a numerical value in the range of 0<x≦0.2)2. b in composition formula (I) is 10^-^4
The radiation image conversion method according to claim 1, wherein the numerical value is in the range of ≦b≦10^-^2. 3. a in compositional formula (I) is 0.25≦a≦6.0
2. The radiation image conversion method according to claim 1, wherein the numerical value is in the range of . 4. 2. The radiation image conversion method according to claim 1, wherein M^III in the compositional formula (I) is Ba. 5. x and X' in the composition formula (I) are each
The radiation image conversion method according to claim 1, characterized in that the material is either Cl or Br. 6. In the composition formula (I), x in 10^-^5≦x≦
2. The radiation image conversion method according to claim 1, wherein the value is in the range of 10^-^1. 7. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is an electromagnetic wave in a wavelength range of 500 to 850 nm. 8. 2. The radiation image conversion method according to claim 1, wherein the electromagnetic wave is a laser beam. 9. In a radiation image conversion panel substantially composed of a support and a stimulable phosphor layer provided on the support, the stimulable phosphor layer is composed of two compounds represented by the following compositional formula (I). 1. A radiation image conversion panel comprising a valent europium-activated alkaline earth metal halide phosphor. Composition formula (I): M^IIX_2・aM^IIX'_2・bSiO:xE
u^2^+...(I) (However, M^II is at least one kind of alkaline earth metal selected from the group consisting of Ba, Sr, and Ca; X and X' are both CL, Br, and at least one halogen selected from the group consisting of I, and X≠X'; and a is 0.1≦a≦10.0
b is a numerical value in the range of 0<b≦3×10^-^2, and X is a numerical value in the range of 0<X≦0.2)10. b in compositional formula (I) is 10^-^4≦
The radiation image conversion panel according to claim 9, characterized in that b is a numerical value in the range of 10^-^2. 11. a in compositional formula (I) is 0.25≦a≦6.0
10. The radiation image conversion panel according to claim 9, wherein the radiation image conversion panel has a numerical value in the range of . 12. 10. The radiation image storage panel according to claim 9, wherein M^II in compositional formula (I) is Ba. 13. 10. The radiation image storage panel according to claim 9, wherein x and x' in compositional formula (I) are each CL or Br. 14. x in compositional formula (I) is 10^-^5≦X≦1
The radiation image conversion panel according to claim 9, characterized in that the value is in the range of 0^-^1.